Fig. 4
From: Experimental observation of photonic nodal line degeneracies in metacrystals
Transformation from nodal line to Weyl points. a When only plasma is applied to the metacrystal without a biased magnetic field, the nodal line (NL) is still present, but blue-shifted to 25 GHz. The plasma frequency is 10 GHz, rendering a photonic band gap at lower frequencies. b A magnetic field is applied parallel to the Γ–X direction, as shown in the inset. This configuration leaves band crossings of the NL on the Γ–X high symmetry line still closed, but gapped elsewhere. Hence two type-I Weyl points are formed in the Brillouin zone
